The present invention relates to computer networks in general, and more particularly relates to methods and apparatus for automatically connecting a Dynamic Host Configuration Protocol (DHCP) client network device to a Virtual Local Area Network (VLAN).
With the proliferation of local area networks (LANs), the need has developed for more powerful tools to manage LANs as they increase in complexity and size. One technique used for managing large networks involves defining one or more virtual local area networks (VLANs), allowing end-user network devices, also referred to herein as xe2x80x9cendpoints,xe2x80x9d to be logically grouped together and communicate as if they are on a common LAN, whether or not they reside on the same physical LAN segment. Some VLAN implementations allow for network switches to automatically identify an endpoint as it is physically attached to a switch port and assign it to a VLAN, either according to a default policy or in accordance with a predefined relationship between the endpoint address and a particular VLAN. In this manner an endpoint may be moved from one physical LAN segment to another while preserving its association with a particular VLAN.
VLANs may be implemented in various types of networks, including Asynchronous Transfer Mode (ATM) networks. Where non-ATM-based networks communicate via ATM networks, LAN Emulation (LANE) may be employed to provide address resolution between ATM and non-ATM addresses, such as Media Access Control (MAC) addresses. Where VLANs and LANE are both used in an ATM network, a network switch to which a non-ATM endpoint is attached may establish a LAN Emulation Client (LEC) to support communications between the non-ATM endpoint and another non-ATM endpoint in a given VLAN. A switch may simultaneously support multiple LECs for multiple VLANs, adding a LEC as communication via a VLAN is requested by one or more endpoints that belong to the VLAN, and removing the LEC when communications over the VLAN are concluded or idle for a period of time.
Further complicating the management of a VLAN/ATM/LANE environment is the need to support endpoints which dynamically request the assignment of their network addresses in accordance with the Dynamic Host Configuration Protocol (DHCP). When a DHCP endpoint is attached to a network it attempts to find a DHCP server which offers the endpoint an address for its use. A DHCP endpoint that does not find a DHCP server within a predefined period will xe2x80x9ctime outxe2x80x9d and cease its attempt to find a DHCP server. Unfortunately, this timeout period is usually much shorter than the time it takes to map a DHCP endpoint upon being connected to a switch port to its VLAN and establish a LEC for the VLAN, thus virtually guaranteeing a DHCP timeout.
The present invention seeks to provide methods and apparatus for automatically connecting a Dynamic Host Configuration Protocol (DHCP) client network device to a Virtual Local Area Network (VLAN) that overcome disadvantages related to the prior art.
There is thus provided in accordance with a preferred embodiment of the present invention a method for automatically connecting a DHCP endpoint to a VLAN in an ATM network having a switch operative to provide LAN emulation for a plurality of non-ATM endpoints, the method including the steps of maintaining a LEC for the VLAN in the absence of any request by any of the endpoints to communicate via the VLAN, the LEC has been previously-established for the VLAN, connecting the DHCP endpoint to a port of the switch, determining a predefined association between the VLAN and either of the address of the port and the network address of the DHCP endpoint, and mapping either of the network address of the DHCP endpoint and the address of the port to the LEC for communication via the VLAN.
Further in accordance with a preferred embodiment of the present invention any of the maintaining, determining, and mapping steps are performed by the switch.
Still further in accordance with a preferred embodiment of the present invention the determining step is performed by a network management station and the method further includes the steps of requesting the network address of the DHCP endpoint from the DHCP endpoint via the switch, and communicating the determination of the predefined association between the VLAN and either of the address of the port and the network address of the DHCP endpoint to the switch.
Additionally in accordance with a preferred embodiment of the present invention the network address of the DHCP endpoint is a MAC address.
Moreover in accordance with a preferred embodiment of the present invention the method further includes the steps of maintaining a plurality of LECs for a plurality of VLANs in the absence of any request by any of the endpoints to communicate via any of the plurality of VLANs, the plurality of LECs have been previously-established for the i of VLANs, and discontinuing maintenance of a least-recently used one of the plurality of LECs.